The SVF in our 1U ‘filter core’ format.
This is a two pole multimode filter capable
of high pass, low pass, band pass and notch output modes. All
four outputs are available simultaneously. This new version of
the very popular Oakley design is based around the classic two
pole state variable filter topology as used in a variety of
vintage synths including the Oberheim SEM and OB-X. At high
resonance the Oakley SVF will oscillate over the whole of the
audio band and is temperature compensated.
The design is intended to fit into a 1U
wide ‘filter-core’ module or a more fully featured 2U wide panel
with seven control pots.
The 1U ‘Filter Core’ format is our
way of handling filter modules. Although the 1U module can be
used as a filter module on its own, it is expected that users
will make use of external mixers to control CV and audio levels
going into the filter. In this way, you will be able to have a
collection of space saving 1U filter cores that can be used with
any generic mixer module. The Oakley Multimix is an ideal choice for a handy mixer
module.
The SVF in the suggested full 2U format.
For the 2U design three audio inputs are
provided each with its own attenuator. Three CVs can control the
cut-off of the filter. One is fixed at 1V/octave, the other two
have input attenuators. CV1 features a reversible type attenuator
with inverting/non-inverting properties.
For DIY builders of this
module it is possible to purchase the Sock8 circuit board which
is available separately. This little board speeds up the wiring
of the eight 1/4″ sockets and reduces the chances of any
wiring errors.
Power (+/-15V) is provided to
the board either by our standard Oakley 4-way header or
Synthesizers.com header. Current consumption is approximately 30mA
per rail.
The issue 5.2 board size is
104 mm (high) x 99mm (deep).
The 1U version behind a natural finish
Scheaffer panel. Note the use of the optional Sock-8 board to
make wiring the socket field much easier.
Sound Samples
All the following samples
recorded with a small set up comprising of two sawtooth VCOs, one
SVF filter, two ADSR/VCA and a midiDAC to control them all. All
the sounds were recorded without any effects added.
Using the low pass
output. Two simple one note hits with the SVF set to medium to
high resonance.
Using the band pass
output. Two more simple one note hits with the SVF set to medium
to high resonance.
Using the -12dB/octave
low pass output. Simple 16th note sequence with an input from the
sawtooth output of a single Oakley VCO. The
filter is manually being swept via the ‘freq’, ‘resonance’ pots
and altering ADSR sweep depth.
Using the notch
output to give a phaser type effect. The SVF is driven from a
triangle wave output from a VCO, first fast, then slow and then
fast again.
This one may make you
jump – watch your volume levels. This sample is using the low
pass output and with the SVF set to full resonance to give self
oscillation. The SVF is modulated by a swept sawtooth VCO and an
ADSR.
Project Downloads
Construction
Guide Our handy guide to building
Oakley DIY projects
Parts
Guide Our handy guide to buying
parts for Oakley DIY projects
Links to schematics are
available to purchasers of the PCB or module and will be sent via
e-mail when the board(s) are shipped.
Front Panel database
A Schaeffer front panel can be made for
this module. The databases can be found by downloading the
following links:
5U format filter
core module in traditional black
5U format filter
core module in natural silver
5U format full width
module in traditional black
To read these files you will need
a copy of ‘Frontplatten designer’ from Schaeffer. The program also features on-line ordering, so its
now even easier to buy your panels from Scheaffer.
The company are based in Berlin in Germany
and will send out panels to anywhere in the world. Delivery to
the UK normally takes around ten days. For North American users
you can also order your Schaeffer panels from Front
Panel Express.
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